This application claims the priority of German Patent Application Serial No. 101 09 206.7, filed Feb. 26, 2001, the subject matter of which is incorporated herein by reference.
The present invention relates, in general, to directional control valves for directing a flow of fluid under pressure to a point of application, and more particularly to a pneumatic multiway valve of a type having a valve housing provided with outer ports for controlling the fluid flow between the ports.
German Pat. No. 44 00 760 A1 discloses a multiway valve which has a valve housing formed interiorly with a valve bore which extends axially through the valve housing and includes grooves for receiving sealing rings in axially spaced-apart disposition. Mounted in the valve bore is a valve spool arrangement which is moveable in a longitudinal direction by a pilot piston, when the pilot piston is acted upon by a control pressure, so as to regulate the supply of fluid under pressure to two outer working ports. The sealing principle involved here is static as the sealing rings are retained by the valve housing. Another sealing concept is known in which the sealing rings are held within grooves by the valve spool.
The valve spool arrangement according to German Pat. No. 44 00 760 A1 includes two separate valve spools, whereby each valve spool interacts with one of both separate working ports. The valve spools are jointly arranged behind one another in coaxial disposition in the valve bore, which extends continuously from one end to the other end, and are moveable in longitudinal direction independently from one another, when acted upon respectively by a control pressure. In this manner, the function of two separate multiway valves can be realized in a single valve housing. Each of the two valve spools is able to carry out in the common valve housing a 3/2 way valve function, whereby each valve spool has its own vent port and both valve spools communicate with a common supply port adjacent to the confronting ends of the valve spools in mid-section of the valve bore.
This conventional multiway valve can also be modified by replacing the two valve spools with a single-piece valve spool which is fitted in the valve bore in order to realize a 5/2 way valve function of a 5/3 way valve function.
This or similar types of multiway valves with valve spool arrangement suffer shortcomings as the valve bore extends along the valve housing to accommodate the valve spools in coaxial disposition, so that the valve housing of the multiway valve exhibits a pronounced elongated configuration which is unfavorable and defeats the desire of realizing a compact design of the valve housing.
It would therefore be desirable and advantageous to provide an improved multiway valve to obviate prior art shortcomings and to realize a compact configuration of the valve housing useful for different valve functions.
According to one aspect of the present invention, a multiway valve for controlling a flow of fluid under pressure, includes a valve housing having fluid ports and a plurality of bores in side-by-side parallel disposition substantially at a same level for accommodating valve spools in one-to-one correspondence, wherein neighboring end faces of the spools are acted upon by actuating means for moving the spools in a longitudinal direction to thereby control a flow of fluid under pressure between the ports, while the opposite end faces interact with a mechanical coupling mechanism secured to the valve housing.
The present invention resolves prior art problems by departing from the conventional teaching of a single continuous valve bore and providing instead several valve bores for respectively accommodating several valve spools which are linked together by a mechanical coupler. As a result, the valve housing can be configured compact. Each valve spool has a defined linkage end face intended to cooperate with the mechanical coupler, and a defined actuation end face intended to interact with the actuating means for axial displacement of the valve spool.
According to another feature of the present invention, the coupling mechanism may be configured as rocker having opposite ends configured for interaction with the coupling end faces of the spools in order to realize a 5/2 way valve function or 5/3 way valve function. As a consequence of the linkage of the spools by the rocker in this fashion, the valve spools are precluded from independently moving relative to one another. Suitably, the ends of the rocker may have a substantially spherical configuration to optimize a force flow as the rocker rests in mid-section against the end faces of the spools. Of course, it is certainly also conceivable to configure the rocker ends in a different manner, so long as the mechanical linkage results in an optimum force flow. Examples include a pointed configuration or arched configuration of the rocker ends.
The multiway valve according to the present invention can be made as part of a valve assembly kit to suit the way valve function to the customer""s needs. According to another aspect of the present invention, the coupling mechanism may be replaced by return springs which act, respectively, on the second end faces of the spools in one-to-one correspondence in order to operate the multiway valve with two 3/n way valve functions. The coupling mechanism or the return springs, depending on the selected option, can be accommodated in a common chamber, which is formed in the valve housing and closed by a lid detachably mounted to the valve housing to ensure accessibility and protection against environmental impact.
According to another feature of the present invention, the actuation for each valve spool is configured as a piston-and-cylinder unit, whereby the piston thereof is connected to the first end face of the valve spool and reciprocates in a cylinder formed by the valve housing. The piston may be connected in one piece to the first end face of the spool. The cylinder of the piston-and-cylinder unit thus defines a control chamber, whereby the axial displacement of the valve spool may be implemented through incorporation of a pilot valve for applying a suitable operating pressure in the control chamber. Suitably, the pilot valve may be so secured to a base of the cylinder as to sealingly close the control chamber. The arrangement of the pilot valve on the cylinder housing permits direct access to the valve bore for mounting or dismantling the valve spool, without requiring additional housing components to close the control chamber.
According to another feature of the present invention, at least one control chamber may accommodate a return spring to provide a passive return movement of the spool and thereby eliminate the need to apply a control pressure in the control chamber via a pilot valve. In this case, it is sufficient to admit fluid under pressure into only one control chamber in order to move the valve spools. The return movement is automatic, when the control chamber is vented.
According to another feature of the present invention, the piston may be disposed in axial offset disposition to the spool in order to allow configuration of a partition wall of minimum wall thickness between neighboring the valve bores. The arrangement of the piston upon the valve spool allows configuration of the valve housing with minimum outer dimensions.
As an alternative to the configuration of the actuation in the form of a piston-and-cylinder unit, the actuation of each of the valve spools may also be implemented by a solenoid with an armature movable in a longitudinal direction and interacting with the valve spool for axial displacement.
According to another feature of the present invention, at least the valve housing may be made of plastics through an injection molding process such that the bores are simultaneously formed. In this way, the need for an additional working step to form the bores through a material-removing process is eliminated. Of course, also the valve spool may be made of plastics in an economical manner.